Video transmission or video streaming within communication networks, such as ISDN networks or the Internet has become an important application of such communications networks. In the future, packet oriented mobile networks like GPRS (General Packet Radio Service) and UMTS (Universal Mobile Telephone Standard) will be commonly used to connect mobile users to fixed communication networks like the above-mentioned ISDN networks or the Internet. It is therefore important to employ efficient and intelligent support of high quality video streaming into wireless radio networks.
A radio channel is a critical resource since its bandwidth is limited. Furthermore, it is a highly unreliable data channel, which requires special techniques to obtain a desired quality-of-service. Additionally, packet switched wireless networks provide variable user data rates depending on the number of concurrently ongoing communications within the same cell.
In order to support data applications (such as file transfer etc.), which require a reliable data link, a combination of forward error correction (FEC) and retransmission-based automatic repeat request (ARQ) is commonly used.
Compared to reliable data transmission, video streaming has rather different requirements. Namely, video streaming is usually less sensitive against data losses, but very delay sensitive. Data transmissions have opposite characteristics, i.e. they are very sensitive to data loss, but not very sensitive to delay. In other words, in the case of video streaming, the loss of certain parts will lead to a certain deterioration of picture quality, which is usually tolerable to a certain degree, but a strong delay (as for example caused by packet retransmission) will require complicated buffering mechanisms and make real-time transmission impossible. Therefore, video streaming is typically conducted by adjusting appropriate parameters, such that the data rate of the video transmitter (for example a video coder) can be easily adapted to the available transmission bandwidth. For example, the input rate of video data into a coder can be controlled, the coding mode can be controlled, or the amount of overhead employed for error correction, such as forward error correction, can be controlled. Existing wireless transmission schemes in mobile networks neither address the special requirements of video streaming nor the advantages resulting from the ability to control the bit rate of a video data source in an appropriate and efficient way.